Semiconductor devices, such as ICs and LSIs, have been often used for providing electronic apparatuses with a high versatility and a small size. Such semiconductor devices, however, exhibits small resistance to abnormal voltages, produced due to, for example, noise, pulses and static electricity.
In order to increase the resistance to the abnormal voltages, multilayer ceramic electronic components, such as multilayer chip varistors, are used. Such semiconductor devices have had high performance and high operation speeds, and accordingly, had small resistance to abnormal voltages. Accordingly, protecting device, such as varistors having low varistor voltages, has been required.
Electric signals of these electronic apparatuses have frequencies of several MHz order. Varistors having small capacitances has been required to being prevented from influencing waveforms of the signals having such high frequencies.
Japanese Patent Laid-Open Publication No. 11-3809A discloses a varistor having a small capacitance. The varistor includes a varistor coating layer and a support layer with a low dielectric constant for supporting the varistor coating layer.
When the varistor coating layer is sintered unitarily with a ceramic layer functioning as the support layer made of material different from that of the varistor coating layer, a defect may be produced at the interface between the varistor coating layer and the ceramic layer, thereby reducing reliability of a chip varistor. During a firing process, additives, such as Bi2O3 and Sb2O3, with a low melting point included in the varistor coating layer may diffuse in the ceramic layer, accordingly reducing characteristics of the varistor coating layer as a varistor.